Twisted intramolecular charge transfer (TICT) excited states: Energy and molecular structure

Abstract

Numerous compounds of donor (D) - acceptor (A) type, in the excited singlet state undergo a relaxation to a highly polar state, preferentially in fluid polar solvents. Study of the rigid model molecules revealed the polar state to correspond to the D and A moieties mutually twisted by 90° To find another proof for the structure of the TICT states, the energies of their emission were calculated for 18 molecules starting from the TICT model. The calculated values are compared to the “polar” fluorescence maxima. The correlation may serve as a structural proof for the TICT states. The structural principle for these states seems to involve a condition of minimum overlap between the D and A orbitals involved in the electron transfer. © 1983 IUPAC